This invention relates to novel waterproofing sealants which are in the form of a pre-formed sheet-like structure. The present sheet-like structure permits application to a substructure surface with overlapping in a manner which gives good mastic to mastic bonding to assure sound waterproofing seals without the need for a protective sheet on the free mastic surface.
It is known that substructural surfaces and the like, such as those formed of concrete, can be sealed in a waterproof manner by forming thereon a continuous membrane of a bituminous composition which is substantially impermeable to moisture. The term "bituminous composition" as used in the present disclosure refers to compositions based on tar, asphalt or pitch, with or without added components. In the past such waterproofing membranes have been formed by in situ application of a hot bituminous composition or of a cold solution or emulsion of bitumen, tar or pitch.
These known methods suffer serious disadvantages. The procedures require the formation of the layer of waterproofing sealant at the job site which does not permit the assurance of a uniform application nor of a resultant uniform layer. In addition, such application causes additional expenses of labor at the job site. Finally, application of such waterproofing sealants to vertical substructural members is both tedious and unmanageable.
More recently waterproofing of substructural members has been accomplished by the application of preformed, flexible membranes of waterproofing pressure-sensitive adhesives such as those disclosed in U.S. Pat. Nos. 3,741,856, 3,853,682, and 3,900,102. These waterproofing materials have a laminate structure comprising a sheet-like support member having a membrane of a flexible bituminous composition superimposed thereon. The bituminous composition may be single or multilayered and has adhesive properties which render it adherent to the support and to the substrate material to which it is applied.
Generally, known preformed waterproofing structures have a support sheet and a membrane of bituminous composition which are coextensive and, in addition, have a protective sheet on the free surface of the membrane which must be removed upon application of the waterproofing structure to the substructure. Formation of a waterproofing seal between courses of preformed waterproofing structures is presently attempted by overlapping the courses and relying on the membrane cold flowing beyond the edge of the support sheet to bond with the free mastic surface of the lapped structure. Such bonds are apt to be defective because of poor intimate contact.
Waterproofing structures have been formed with mastic membranes extending short distances beyond the support sheet to yield a partially exposed surface. These require a protective sheet on the free surface of the mastic to prevent its bonding with the partially exposed surface during packaging and storage. Such protective sheets present the problems of removal and disposal at the job site of the additional protective sheet.
Some structures, such as disclosed in U.S. Pat. No. 4,039,706, have their free major surface formed of a nonadherent material and rely on the application of multiple layers of the structure on the subsurface in an attempt to achieve adequate waterproofing. The second and subsequent layers can be applied parallel to each other with any one course of a layer overlapping the seam formed by the two adjacent courses of the previously applied layer or the layers can be applied in a criss-cross manner with respect to the previously applied layer. The release sheet may be perforated to enable its removal at one time or to permit tearing of such sheets for its removal in sections as the next layer of waterproofing structure is being applied. These structures have the drawbacks of requiring the application of multiple layers in an attempt to achieve waterproofing. Such multilayer application is costly due to the amount of material used and to the labor required. Further, because the free major surface of the structure is of a non-adherent material, one can not be assured, even after application of multiple layers, of obtaining satisfactory waterproofing. In addition, the problems of removal and disposal of the release sheet at the job site are compounded by the required application of multiple layers.